An emerging area of interest in computer technology is to provide machine-vision based user input to a computer system. A suitably configured machine-vision system can acquire live video of a user, enabling the user's face to be recognized, his gestures analyzed, and so on. Output from the machine-vision system may be fed into a computer system, where it provides various control functions—launching an application, controlling the movements of a game character, etc.
Another form of user input that can be captured via machine vision is the user's ocular state, which includes gaze direction and focal plane. Such capture requires accurate imaging of the user's eyes. To this end, each eye may be illuminated in a controlled manner with light that is reflected into the machine-vision system to reveal the orientation of the eye.